1. Field of the Invention
The invention relates to a protective circuit for protecting an input or an output of an electrical apparatus from an overvoltage.
The invention further relates to an automation component having an electrical apparatus for automating industrial processes, which includes an input or output channel.
2. Description of the Related Art
Protective circuits for protection against electrical circuit parts of an electrical apparatus are already known. One of the most frequent, currently known protective circuits consists of two diodes, which are connected on the one hand to the input against a positive potential and on the other hand to the input against a negative potential. This circuit is known to the person skilled in the art as a “clamping” diode circuit, and it is used to limit the voltage to a positive and to a negative voltage. To this end, a first diode rests with its anode on the input to be protected and a second diode rests with its cathode on the input to be protected. A resistor is also in series with the input to be protected.
This protective circuit is disadvantageous in that the series resistor introduced into the signal path of the input is generally highly resistive, which has an unfavorable effect on signal currents to be detected across the input.